Posted by Ron on November 19, 05 at 13:26:25:
In Reply to: Question posted by Ron on November 19, 05 at 13:08:18:
I went here. It spun 32 3/4 times which is a 4:10 =)
http://www.tfrecord.com/pages/page22.html
: I jacked suburban up. I spun the tire 1 full turn and the drive shaft spun 2 times.
: : Maybe I remember wrong then (regarding RPM?). I see your point. I'll check the gears when they do a gear fluid change or isn't there a way to tell before then? Only thing would be if someone put 3:73 gears in a 4:10 box then. Again, I watched them the hole time
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: : : Ok, I admit I am not that savy on gears and such, however, if the RPM's & speed are the same then what did you gain by making the switch???
: : : The change was about a 10% difference. I think your speedo is now off by that amt., if they made the correct change. Maybe they put the same ratio in?
: : : I remember doing the old hotrod change and the speedo showed like 70 and I was only going 60.
: : : Get a portable GPS and check your speed.
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: : : : Ps. According to the few tire/gear calcs I did on-line, it should have only changed the rpm 200. Maybe this is why? I really don't see that on the tach?
: : : : : What? Has anyone changed their's that can chime in? I saw the box and whatched them do it. I never left the shop. I can tell the difference 100%!
: : : : : I know this, when I had my '89 suburban and went with the 265/70/16 and changed the 3:73 to a 3:42 I went to have the speedo checked in Riverside, Ca. they put it on a dyno or something and said the speedo was off 1mph! Remember? I posted it. So, maybe the change in the other direction is the same not much difference. I'll take pics of gear and pinion and they do the fluid change to show it's a 4:10
: : : : : : : I didn't change the speedo "re-calibrate". I watched them change everything out. I went to DTD as a few here have (same place I did the '89 suburban). It took them 4hrs. I watched them the whole time.
: : : : : : : : : : Changed the rear from 3:73 to 4:10. What a difference! No rpm change at all. Still 2300 @ 80mph. Would do it again... DriveTrainDirect.com did a great job as always (They did my other suburban).
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: : : : : : : : : If no rpm and speedo change and the same tire dia, then you got ripped off...it's the same gear ratio.
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: : : : : : : : This is assuming you had the speedo re-calibrated. You did right?
: : : : : : : : Otherwise any change in diff gearing will still have the speedo & tack read exactly the same, as they are reading it "before" the diff.